[SustainableTompkins] Weeds - threat or mentor in warming world?

[Adele Gay Nicholson]

Tompkins County has its share of invasive plant species, and our  
pollen counts are escalating with the increase in CO2 levels.  Very  
interesting to think of weeds just filling the niches that our  
activities have opened - passengers, not drivers of native species  
loss (see below).

(I hope kudzu never reaches here, but at least it might be good for  
making ethanol!)

Gay



NY Times June 29, 2008


*Can Weeds Help Solve the Climate Crisis? *

By TOM CHRISTOPHER

Lewis Ziska, a lanky, sandy-haired weed ecologist with the Agriculture  
Research Service of the U.S. Department of Agriculture <http://topics.nytimes.com/top/reference/timestopics/organizations/a/agriculture_department/index.html?inline=nyt-org 
 >, matches a dry sense of humor with tired eyes. The humor is  
essential to Ziska?s exploration of what global climate change <http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html?inline=nyt-classifier 
 > could do to mankind?s relationship with weeds; there are many days,  
he confesses, when his goal becomes nothing more than not ending up in  
a fetal position beneath his battleship gray, government-issue desk.  
Yet he speaks of weeds with admiration as well as apprehension, and  
even with hope.

It is easy to share the admiration and apprehension when you consider  
the site that Ziska planted with weeds in downtown Baltimore in the  
spring of 2002. Tucked in next to the city?s inner harbor, the site is  
part of a barren expanse of turf rolled out over a reclaimed  
industrial landscape. This unfertile scrap seems an unlikely choice  
for growing anything, but Ziska saw in it, ominously perhaps, a model  
of where the global habitat as a whole is headed.

?Ingenuity,? Ziska says, ?may be the mother of invention, but poverty  
is definitely the father.? For some time, he had wanted to create in a  
laboratory setting the elevated temperatures and increased  
concentrations of atmospheric CO2 predicted for the mid-21st century  
by the Intergovernmental Panel on Climate Change, the leading  
international scientific authority on the subject. Carbon dioxide has  
received a lot of attention as a greenhouse gas, a major cause of  
global warming. But it is also, along with water, light and nutrients,  
one of the four essential resources for plant growth. The effect that  
boosting this gas?s concentration in the atmosphere will have on  
plants is very poorly understood.

The facilities for testing the effects of CO2 enrichment in Ziska?s  
lab on the U.S.D.A. research campus in Beltsville, Md., were limited.  
His best option there was a growth chamber, essentially an airtight,  
climate-controlled, artificially lighted aluminum box about as  
spacious as a walk-in closet. Ziska had something more ambitious in  
mind, but his budget, which has been cut repeatedly by an  
administration seemingly intent on minimizing attention to global  
climate change (his lab has been reduced to 3 researchers who study  
climate change and agriculture, from 10 in 1999), wouldn?t support the  
construction of special facilities. Then it occurred to Ziska that the  
complaints made by residents of nearby Baltimore about summer in their  
city  the exhaust-laden air and the way in which buildings and  
pavement soak up solar energy <http://topics.nytimes.com/top/news/science/topics/solar_energy/index.html?inline=nyt-classifier 
 > to create an abnormally warm ?heat island?  could be put to good  
use. When he checked, he found that in fact the temperatures in  
Baltimore run 3 to 4 degrees Fahrenheit warmer on average than those  
of the surrounding countryside, and the concentration of CO2 in the  
local atmosphere (440 to 450 p.p.m., or parts per million by volume)  
is well above the current global average. This, coincidentally,  
matched almost exactly what the panel on climate change predicted for  
the planet as a whole 30 to 50 years in the future in its ?B2  
scenario,? a middle-of-the-road projection that envisions continuing  
greenhouse gas increases but also some success in abatement programs.

By comparing three sites  an organic farm in western Maryland, a park  
in a Baltimore suburb and the one by the inner harbor  Ziska planned  
to study three circumstances: the present (on the organic farm), the  
mid-century future as predicted by the climate-change panel (in  
Baltimore) and something in between (the suburban site). He took soil  
from the organic farm, which already contained seeds of 35 common  
weeds, and with it created uniform beds at each of the sites, urban,  
suburban and rural, so that the growing medium and weed population  
would be the same throughout. What happened over the next five growing  
seasons surprised even him.

Not only did the weeds grow much larger in hotter, CO2-enriched plots   
a weed called lambs-quarters, or Chenopodium album, grew to an  
impressive 6 to 8 feet on the farm but to a frightening 10 to 12 feet  
in the city  but the urban, futuristic weeds also produced more  
pollen. Even more alarming was the way that the increased heat and CO2  
accelerated and perverted the succession of species within the plots.  
Typically, a cleared area in the Eastern United States, if left to  
itself, returns to native woodland. This process varies with the site  
and circumstances, but in its archetypical form fast-growing annual  
weeds cover the soil first, playing the role of what ecologists  
classify as ?pioneer plants.? These gradually give way to longer-lived  
perennial weeds, which are in turn replaced by shrubs and trees.

In the natural version of this process, the pioneers and their  
successors are species indigenous to the area, and the woodland?s  
restoration takes decades. But what Ziska observed in his urban plots  
was ecology on amphetamines, a nearly completed succession to trees by  
the end of five years, with a domination by invasive weed trees of the  
most troublesome sort: ailanthus, Norway maples and mulberries. Five  
years after the creation of the plots, the biggest ailanthus in the  
rural test site measured about five feet tall. The city site boasted a  
20-footer. The suburban plot was following the city?s lead, though it  
lagged a couple of years behind.

As a scientist, Ziska was excited by his experiment?s striking  
outcome. As someone who has spent his career battling weeds, though,  
he was frightened by the implications. Weeds already cost U.S. farmers  
about 12 percent of their harvest, exacting an estimated annual loss  
of $33 billion. What would be the additional cost in the future, not  
only to farmers but also to foresters, land managers and gardeners, of  
beating back supercharged weeds? Still, even as he contemplated this,  
Ziska says he couldn?t repress a certain admiration. He traces his  
interest in weeds to an epiphany during his undergraduate years at the  
University of California at Riverside: noticing a weed springing up  
through a crack in the Southern California pavement, he was suddenly  
struck with wonder at any organism that could flourish in such a hot,  
dry, hostile environment. That may become an essential talent, it  
occurred to Ziska, given the way our planet is going.

*Taking the long view*, it becomes apparent that the events in Ziska?s  
plots were just another twist in the more than 10,000 years of joint  
history, ours and the weeds?. We have been intimately linked since  
Neolithic times, for in a fundamental sense weeds are a human  
creation. ?Weed? is a subjective label applied as a matter of personal  
judgment, a point that becomes obvious when you consider how many ? 
noxious weeds?  plants now marked for destruction by federal, state or  
county authorities  were deliberately introduced into North America by  
individuals convinced of their beauty or utility. The ailanthus tree,  
for example, currently regarded as one of the most troublesome weeds  
of our urban habitats, was brought from China to eastern North America  
in the 19th century for use as a fast-growing shade tree and is said  
to have been introduced into California by Chinese immigrants who  
valued its medicinal properties.

There are countless definitions of weeds, ranging from the hardheaded  
one necessarily observed by farmers, that a weed is any plant that  
interferes with profit, to the aesthetic (a popular gardener?s  
definition of a weed is ?a plant out of place?), to Ralph Waldo  
Emerson <http://topics.nytimes.com/top/reference/timestopics/people/e/ralph_waldo_emerson/index.html?inline=nyt-per 
 >?s sanctimonious assertion that a weed is ?a plant whose virtues  
have not yet been discovered.? But all agree on the central criterion:  
to qualify as a weed, the plant in question must be viewed with  
disfavor by humanity. Simply put, any plant, if we dislike it, becomes  
an intruder in our landscape and so a weed.

Arguably, then, there was no such thing as a weed until mankind  
developed the need to discriminate, which came with the development of  
agriculture in the Neolithic era, around 9,000 B.C. In fact, many of  
the wild grains like red rice or wild oats that are among our most  
troublesome agricultural weeds today were valued food sources until we  
graduated from the hunter-gatherer stage of our existence.

Much has been made of our scientific triumph in breeding modern crop  
plants from those wild ancestors. The transformation of an east Asian  
wild grass (red rice) into the crop that provides 20 percent of  
humanity?s caloric intake is extraordinary. What generally goes  
unrecognized, though, except among weed scientists, is the extent to  
which we also made weeds what they are.

Coexistence with mankind has given rise to the sort of tough plants  
that flourish despite the worst we can do  hoeing, pulling, burning  
and, more recently, spraying the fields with herbicidal chemicals.  
Weeds have adapted to every means we used to exterminate them, even  
turning the treatments to their own advantage. Attacking a Canada  
thistle (actually of Eurasian origin and a regular entry in ?worst  
weeds of North America? lists) with hoe or plow, for example, may  
destroy the plant?s aboveground growth but leaves the soil full of  
severed bits of fleshy root, each of which may sprout a new plant.

A result of this history is that crops and weeds embody diametrically  
opposed genetic strategies. Over the centuries, we have deliberately  
bred the genetic diversity out of our crop plants. Creating crop  
populations composed of clones or near clones was an essential step in  
achieving higher yields and the sort of uniform growth that makes  
large-scale, mechanized cultivation and harvesting possible. Because  
weed populations live as opportunists, however, they must include  
individuals with the ability to flourish in whatever type of habitat  
we make available. They also need diversity to cope with the wide  
range of punishments we inflict. A patch of Canada thistles, if it is  
to survive when the farmer switches from hoeing to herbicides, must  
include individuals that develop a resistance to the chemicals over  
time. Weed populations that lacked the necessary genetic diversity  
faded from our fields, lawns and waste places; historians of  
agriculture can cite many such casualties.

The survivors are an astonishingly plastic group of plants. James  
Bunce, a plant physiologist with an office down the hall from Ziska?s,  
has been studying the effect on dandelions (that nemesis of the  
suburban greenskeeper) of atmospheres artificially enriched with CO2.  
He found in a series of trials that populations of the familiar weed  
evolve, changing physically to take advantage of this sort of resource  
enhancement, within the space of one growing season.

?When you change a resource in the environment,? Ziska said recently,  
sitting in his compact office, ?you are going to, in effect, favor the  
weed over the crop. There is always going to be a weed poised  
genetically to benefit from almost any change.?

Ziska, together with Bunce, has been testing the effects of changing  
CO2 concentrations on a range of crop and weed species. Wending his  
way through a basement full of pumps, filters and boxlike aluminum  
growth chambers, Ziska showed himself to be a connoisseur of  
atmospheres. Peering at the instrument panel outside one growth  
chamber, he noted a CO2 concentration of 310 p.p.m. ?That?s a 1957  
atmosphere, the year of my birth,? he said. What he and his colleagues  
have found, he said, is that weeds benefit far more than crop plants  
from the changes in CO2 and that the implications of this for  
agriculture and public health are grave.

Tests with common agricultural weeds like Canada thistle and quack  
grass found them more resistant to herbicides when grown in higher  
concentrations of CO2, making them harder to control. Ziska  
hypothesizes that this may be a result of faster growth; the weeds  
mature more rapidly, leaving behind more quickly the seedling stage  
during which they are most vulnerable. This promises to be an  
expensive problem for farmers, who will have to spend more on  
chemicals and other anti-weed measures to protect their crops.  
(Herbicides already cost farmers more than $10 billion annually  
worldwide.)

But enhancing CO2 levels, Ziska has found, not only augments the  
growth rate of many common weeds, increasing their size and bulk; it  
also changes their chemical composition. When he grew ragweed plants  
in an atmosphere with 600 p.p.m. of CO2 (the level projected for the  
end of this century in that same climate-change panel ?B2 scenario?),  
they produced twice as much pollen as plants grown in an atmosphere  
with 370 p.p.m. (the ambient level in the year 1998). This is bad news  
for allergy sufferers, especially since the pollen harvested from the  
CO2-enriched chamber proved far richer in the protein that causes the  
allergic reaction. Poison ivy has also demonstrated not only more  
vigorous growth at higher levels of CO2 but also a more virulent form  
of urushiol, the oil in its tissue that provokes a rash.

According to Ziska, the steady increase in atmospheric CO2 since the  
beginning of the Industrial Revolution may have already had a major  
impact on the growth of at least one supremely costly weed. Cheatgrass  
(Bromus tectorum), a native of central Asia, is believed to have been  
introduced into the United States accidentally, as seeds in soil used  
to ballast ships or as a contaminant in agricultural seed, in the  
mid-1800s. Since then, its ability to flourish in dry habitats and its  
prolific seed production (a single plant can bear as many as 5,000  
seeds) has helped it to overrun 100 million acres of Western  
rangeland, an area larger than the state of Wyoming. In doing so,  
cheatgrass has displaced more nutritious native grasses, reducing the  
quantity of livestock a given acreage can support. Cheatgrass has also  
diminished the land?s value to wildlife, which also finds the  
introduced plant unpalatable.

The spread of cheatgrass has been widely attributed to the degradation  
of native grasslands by overgrazing  cattle prefer and selectively eat  
the native grasses  and more especially to its exceptional  
combustibility. Periodic fires are an integral part of the rangeland  
ecology, but when the rangeland is still dominated by native grasses,  
fires occur in some areas at average intervals of every 60 to 110  
years. In areas overrun by cheatgrass, however, fire sweeps through  
every three to five years. While cheatgrass can tolerate such frequent  
burns, the native flora cannot.

Cheatgrass?s combustibility is inherent in the plant?s pattern of  
growth. Sprouting in the fall, it resumes growth at winter?s end to  
mature and set seed in early summer, whereupon the plant dies, leaving  
a tuft of dry, highly flammable leaves through the following dry  
season. Ziska and his colleagues discovered, though, that the weed?s  
flammability seems to have been greatly augmented by the increases in  
atmospheric CO2 that occurred during the period of cheatgrass?s spread  
through the West.

The scientists grew the plant at four concentrations of CO2: at 270  
p.p.m. (the ambient level at the beginning of the 19th century, before  
the Industrial Revolution), at 320 p.p.m. (a 1960s level), 370 p.p.m.  
(a 1990s level) and 420 p.p.m. (the approximate level predicted for  
2020 in all the climate-change panel?s estimates). What they found was  
that an increase of CO2 equivalent to that occurring from 1800 until  
today raised the total mass of material (the biomass) each cheatgrass  
plant produced by almost 70 percent. In addition, the composition of  
the cheatgrass changed as the CO2 level increased, the tissues  
becoming more carbon-rich so that the plant leaves and stems are less  
susceptible to decay. In a natural setting, this would mean that the  
dead material would persist longer, adding yet more fuel for wildfire.

More fuel, with a longer life  Ziska says that the rise in greenhouse  
gases we have already achieved may have played a decisive role in the  
spread of a weed that has already transformed the ecology of the  
Western United States. The situation seems likely to worsen too. The  
cheatgrass that Ziska grew at the CO2 level equal to that projected  
for 2020 increased the plant?s biomass by another 18 percent above  
current levels. Global climate change, it seems, will further stoke  
the rangeland wildfires.

?*There?s no such thing* as natural selection,? Ziska confides. He is  
not, he hastens to explain, a creationist. He is merely pointing out  
that the original 19th-century view of evolution, the one presented by  
Charles Darwin <http://topics.nytimes.com/top/reference/timestopics/people/d/charles_robert_darwin/index.html?inline=nyt-per 
 > and Alfred Wallace, is obsolete. Their model presented evolution as  
a process taking place in a nature independent of human interference.  
That is almost never the situation today  even at sea, where less than  
4 percent of the oceans remain unaffected by human activity, according  
to a recent article in the journal Science. This interference with  
nature has set the stage for the success of a growing category of  
weeds, one exemplified by cheatgrass: invasive plant species.

These are plants that evolved outside a local or regional ecosystem  
but were at some point released into it, typically by human action.  
Some invasives, like cheatgrass, arrived as hitchhikers and stowaways;  
others, like kudzu, were introduced deliberately. (A Japanese species,  
kudzu was planted by state and federal agencies to control soil  
erosion throughout the Southern states in the 1930s and ?40s.) In any  
case, the invasive plant species share a quality of aggressive,  
explosive growth in their new homes and the ability to outcompete the  
native vegetation of forests, grasslands and wetlands  areas that we  
are accustomed to think of as outside the sphere of human influence.

Popular opinion has treated the invasive plants as botanical illegal  
aliens. The Environmental Protection Agency <http://topics.nytimes.com/top/reference/timestopics/organizations/e/environmental_protection_agency/index.html?inline=nyt-org 
 > has labeled them as the second-greatest threat to the continent?s  
biodiversity, exceeded in their impact only by outright destruction of  
habitat. Major resources have been devoted to the spraying and rooting- 
out of invasive plants in the belief that their removal would enable  
an ecological revival. Roughly $45 million, for example, is spent  
every year in the unsuccessful attempt to stop the spread of a single  
European wetland weed, purple loosestrife (Lythrum salicaria).

New research, however, suggests that invasive species, at least in  
some instances, aren?t so much the causes of environmental degradation  
as eco-opportunists taking advantage of disturbed habitats. Or, as the  
biologist Andrew MacDougall of the University of Guelph, Ontario, puts  
it, the invasives may behave more as ?passengers? than as ?drivers.?  
This is the conclusion he reached in a pair of studies, one of an oak  
savanna in British Columbia and the other of degraded prairie in  
southwestern Saskatchewan.

MacDougall had not intended to focus on invasive plants when he began  
studying a Nature Conservancy <http://topics.nytimes.com/top/reference/timestopics/organizations/n/nature_conservancy/index.html?inline=nyt-org 
 > Canada property on Vancouver Island. An 86 acre remnant of oak- 
studded grassland, this sanctuary exemplified a type of open savanna  
habitat that was once common in the area but that was nearly  
eliminated by agriculture and sprawl. MacDougall?s original interest  
was in the native flora; this Nature Conservancy sanctuary is a  
biodiversity hot spot, hosting more than 100 species of plants and  
animals at risk in British Columbia or nationally.

Despite this land?s protected status, MacDougall found that the native  
plant community was failing, the rarities becoming rarer. The young  
ecologist blamed an invasion by several foreign grasses for this  
decline. Initially, he supposed that simply removing the foreigners  
would prompt a renaissance of the native grasses and wildflowers.

The actual response was quite different. For three years MacDougall  
removed the invasive grasses from plots he outlined within the  
reserve. In some plots, he did this by mowing or burning; in others,  
he removed the weeds entirely. Yet the native flora didn?t rebound  
significantly. In some cases, the decline of the native plant species  
instead accelerated, and the fundamental character of the flora within  
the plots began to change, with woody plants encroaching on the  
formerly open, grassy areas.

MacDougall concluded that rather than serving as drivers of change,  
the foreign grasses were functioning more in the role of passengers,  
merely filling in as the natives disappeared. In fact, the foreigners  
seemed to be serving a stabilizing role. By blocking light from  
reaching the soil, they inhibited the germination of tree and shrub  
seeds. Keeping the brush at bay in this fashion preserved the open  
character of the savanna habitat so that the remnants of the original  
savanna wildflowers, grasses and wildlife could at least survive. In  
light of these findings, MacDougall says, he came to believe that the  
primary cause of the native flora?s decline was human intervention.  
Before European settlement, fire periodically cleansed the soil  
surface of dead plant material. Suppression of fire since settlement  
had allowed a thick layer of litter to accumulate, and the foreign  
grasses cope better with this than do the natives.

The relevance of this discovery to an era of global climate change has  
become apparent in MacDougall?s subsequent research in the  
Saskatchewan prairie. These grasslands were infiltrated with crested  
wheatgrass, a species from the Eurasian steppe. Again, the foreign  
grass was blamed as the driver in the decline of the native flora.  
MacDougall, however, says he believes the invader?s success is largely  
derived from climatic change over the last half-century. Weather  
records reveal that spring warmth in this semiarid region is coming  
earlier than it used to, and the season?s rain is more consistent. The  
wheatgrass, which awakens from winter dormancy earlier than the native  
grass species, has gained a competitive advantage from this change.

MacDougall says he believes that a North American grass species could  
be found that could compete successfully in the altered climate and  
would also (unlike the exotic) interact beneficially with native  
wildlife. He admits, though, that replanting this prairie would be a  
big endeavor, that it would require as much effort as the 19th-century  
pioneers gave to taming the prairie habitat. Whether the will and  
resources exist for this seems questionable, especially as habitat  
disturbance spreads around the globe, creating many similar situations.

MacDougall says he is hopeful that the climatic changes projected for  
this century won?t exceed the tolerance of most native plant species.  
He admits, though, that the spread of the exotics suggests that they  
are more genetically diverse and thus better able to cope with  
environmental change. MacDougall clearly doesn?t like the prospect,  
but he admits he can imagine a future so generally disturbed that we  
may well be grateful for what he calls the ?positive services?  the  
aggressive adaptability  of the botanical aliens.

*It was a Tuesday in early January*, but the temperature in center  
city Philadelphia had reached 65 degrees, and rosettes of dandelion  
leaves were starting to sprout flower buds in the neat bed of mulch  
outside the Sheraton Society Hill hotel. Inside, in a meeting room set  
up with chairs, screen and PowerPoint projector, the membership of the  
Northeastern Weed Science Society was equally disturbed. These are, by  
necessity, conservative people. A mixture of university researchers,  
county agents and representatives of the herbicide industry, the  
attendees had the look of farmers or foresters temporarily off their  
land  clean-cut, tanned, tending toward the wiry. Most looked  
distinctly uncomfortable in crisp sport jackets and polyester blazers  
that, you suspected, had spent the 12 months since the last annual  
meeting in a closet. If the members looked like farmers, that was  
because it is farmers they serve, and they had clearly absorbed the  
wary ethic of that profession in which sudden change, whether of  
weather, markets or government policies, is almost always for the worse.

The day?s news surely confirmed that prejudice. The second day of this  
year?s annual meeting was devoted to a symposium on weeds and global  
climate change, and the speakers were outlining a future in which many  
of the members? current strategies will be irrelevant or ineffective.

The keynote speaker, Cameron Wake of the University of New Hampshire <http://topics.nytimes.com/top/reference/timestopics/organizations/u/university_of_new_hampshire/index.html?inline=nyt-org 
 >?s Climate Change Research Center, did little to put the audience at  
ease. Wake is a charismatic man who has traveled the colder regions of  
the world  the Canadian arctic, the Greenland ice sheet, Antarctica  
and the high mountains of Central Asia. On these trips, he collects  
ice cores, whose analysis enables him to reconstruct histories of past  
atmospheric and climatic changes. His soul patch, pink shirt and pink  
tie made him a minority of one in this room. He dealt firmly with an  
audience member who asserted that the climatic warming is nothing new,  
that records from imperial Rome indicate that citrus and other warm- 
weather crops were then far to the north of their current ranges. Wake  
pointed out that local archaeology can?t change the global data set,  
which proves that the level of CO2 in the atmosphere is at its highest  
point in more than 650,000 years and that the rate of increase is  
accelerating.

Subsequent speakers got down to cases. Andrew McDonald, an  
agricultural scientist at Cornell University <http://topics.nytimes.com/top/reference/timestopics/organizations/c/cornell_university/index.html?inline=nyt-org 
 >, had used the Intergovernmental Panel on Climate Change?s high  
projections for CO2 levels at the middle and end of the century to  
create an atlas of potential weed migrations in cornfields in the  
Eastern United States. If these projections prove accurate, Kentucky,  
by the end of the next one to three decades, should have a climate  
(and weed flora) resembling that of present-day North Carolina; by  
century?s end, it will have shifted to a regime more like that of  
Louisiana. Delaware, over the same period, will be transformed to  
something first like North Carolina and then Georgia, while  
Pennsylvania will metamorphose into West Virginia and then North  
Carolina. Florida will become something unprecedented in this country.  
Field observations indicate that these transformations are already  
under way: another speaker pointed out that kudzu, ?the weed that ate  
the South,? has already migrated up to central Illinois and by 2015  
could be extending its tendrils into Michigan?s Upper Peninsula.

Even more sobering were the figures that the biologist Brent Helliker  
of the University of Pennsylvania <http://topics.nytimes.com/top/reference/timestopics/organizations/u/university_of_pennsylvania/index.html?inline=nyt-org 
 > flashed on the screen. First, he used maps taken from an ecology  
textbook to show the way the last ice age drove various forest types  
southward. Then came a map Helliker created, suggesting that the  
current warming seems most likely to change the ranges to which forest  
trees are adapted  the areas where the black spruce, for example,  
grows now, are likely to become better suited to broadleaf trees. He  
asked the question that was on the lips of every one of his listeners:  
Can the forest adapt so drastically in a space of just decades?  
Helliker announced that he had no answer to that question, and his  
talk was over.

*During a break between talks*, Lewis Ziska was surprisingly upbeat.  
With the challenges, he insisted, come opportunities. Kudzu, for  
instance: Ziska has been seeking financing to study its potential as a  
source of biofuel. Kudzu roots, as much as 50 percent starch by  
weight, seem ideal for ethanol production, while the plant?s  
supercharged vines, which can grow a foot a day, would be an abundant  
source of alternative energy. This would be win-win: we develop an  
alternative to fossil fuels and, at the same time, create a financial  
incentive to root out a particularly troublesome weed.

Developing techniques for managing weeds in a time of global climate  
change will be essential to the world?s agricultural future, and the  
U.S.D.A. researchers, though they have been starved of essential  
financing, lead the world in this field. (There is one exception,  
Ziska admits; his Web searches have revealed that marijuana growers  
have an amazingly detailed knowledge of how CO2 enrichment affects  
their crop. But as Ziska points out, they don?t publish in scientific  
journals.) Possession of this expertise could be a great economic  
asset to the United States, both for the protection it could provide  
to our own harvests and as an intellectual export that is sure to be  
much in demand in other countries.

Ziska says that he worries about mankind?s ability to feed itself in a  
fast-changing future. Paradoxically, it is weeds, he says, that can  
provide solutions. They have helped us deal with lesser crises in the  
past. When diseases and pests overwhelmed our domesticated food crops,  
it was to their wild relatives  plants that mankind has been battling  
for millennia  that plant breeders turned. Because weeds have more  
diverse genomes, it is easier to find one with the proper genetic  
resistance to a given threat  and then to create a new hybrid by  
breeding it with existing crops. An answer to the Irish potato blight  
of 1845-6 was eventually found among the potato?s wild and weedy  
relatives; a wild oat found in Israel in the 1960s helped spawn a more  
robust, disease-resistant strain of domesticated oats.

Weedy ancestors of our food crops, Ziska predicts, will cope far  
better with coming climatic changes than their domesticated  
descendants. Coping, after all, is what weeds have always done best.  
As last year?s climate- change panel report, Climate Change 2007, made  
clear, we have already set in motion far-reaching and unstoppable  
changes in regional temperatures and precipitation and in the  
composition of our atmosphere. No matter what actions we take, these  
changes will continue for decades. If we are to avoid disaster,  
experts agree, we will need to be tenacious but flexible, ready to  
identify and exploit any opportunity in what will be a challenging,  
even hostile situation. In this new world that we have made, weeds,  
our old adversaries, could be not only tools but mentors. At which  
point, if Ralph Waldo Emerson is to be believed, weeds by definition  
will cease to exist.

Tom Christopher writes frequently about horticultural and  
environmental topics.

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----------------------------------------------------
Gay Nicholson, Ph.D.

607-533-7312 (home office)
607-279-6618 (cell)

1 Maple Avenue
Lansing, NY 14882
gaynicholson at aol.com

Sustainable Tompkins
Program Coordinator
www.sustainabletompkins.org

Southern Tier Energy$mart Communities
Regional Coordinator
Cornell Cooperative Extension of Tompkins County
615 Willow Ave., Ithaca, NY 14850
agn1 at cornell.edu